Toneable conduit and method of preparing same

ABSTRACT

The invention is a toneable conduit that can transmit a signal and be readily detected by toning equipment. The conduit can be coupled with other conduit to provide extended lengths of conduit. The toneable conduit includes an elongate polymeric tube having a wall with an interior surface, an exterior surface, and a predetermined wall thickness. A channel preferably extends longitudinally within the wall of the elongate polymeric tube; a stabilizing rib extends longitudinally along the interior surface of the wall of the elongate polymeric tube and is located radially inward from the channel. A continuous wire is coincident with the channel in the elongate polymeric tube and preferably coated with a composition that prevents it from adhering to the polymer melt that forms the elongate polymeric tube. The present invention includes methods of making the toneable conduit and methods of coupling a first toneable conduit with a second toneable conduit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 10/830,754, filed Apr. 23, 2004, which is a divisional of U.S.patent application Ser. No. 10/158,810, filed May 30, 2002 nowabandoned, which is a continuation-in-part of copending U.S. patentapplication Ser. No. 09/989,289, filed Nov. 20, 2001.

FIELD OF THE INVENTION

The present invention relates to toneable conduit and more particularlyto toneable conduit that can be detected by conventional toningequipment and that includes a wire that is capable of being torn out ofthe conduit to allow the conduit and wire to be coupled.

BACKGROUND OF THE INVENTION

Conduit is often buried to provide an underground path for cables suchas coaxial cables and fiber optic cables. In particular, conduit istypically formed of a plastic material that protects the coaxial cablesand fiber optic cables from the moisture and other hazards of theunderground environment. The cable is typically installed in the conduitby pulling the cable through the conduit although the cable can beprovided in the conduit when it is installed underground.

One issue with conduit is that it can be difficult to locate undergroundwhen it is either empty or it contains a non-metallic cable, such as afiber optic cable. As a result, conduit has often been outfitted with ametallic or magnetic strip or wire that allows the conduit to bedetected by metal detecting equipment on the ground surface. Althoughthese types of detection devices are useful, they cannot always locateconduit that is buried deep underground (e.g. greater than 5 feet). Asan alternative to these types of detection devices, toning equipment iscommonly used that operates by transmitting a signal along a metallicwire or strip associated with the conduit and detecting the signal fromthe ground surface.

One conventional conduit construction that can be detected byconventional metal detection devices and even the toning devicesdiscussed above includes an exterior rib that houses the metallic ribbonor wire. For example, Japanese published application JP 5-106765describes an embodiment that includes an exterior rib including aconductive wire. Although these types of constructions have found use,it is difficult to couple this conduit with another conduit because theexterior rib prevents the connector from fitting flush onto the conduit.As a result, moisture can enter the conduit at the connection and cancause damage to the cable installed therein. In addition, the exteriorrib can cause problems during installation in that the exterior rib andassociated wire can be ripped off of the conduit if the conduit is beinginstalled by directional boring or plowing methods.

Another conduit construction that is designed to be detected by metaldetection devices includes a metallic ribbon or wire that is provided atintermittent lengths. For example, U.S. Pat. No. 6,092,558 describessuch an embodiment wherein discrete lengths of a magnetic strip arespaced apart longitudinally along the conduit. U.S. Pat. No. 5,045,368also describes a similar construction having markers at intervals alongthe length of the conduit. Although this type of conduit can be detectedby the metal detection devices discussed above, it cannot be detected byconventional toning equipment because a signal cannot be transmittedalong the conduit.

Alternatively, some conduit constructions use continuous lengths ofstrip or ribbon formed of metal or a magnetic material to allow theconduit to be detected by metal detecting equipment. For example, U.S.Pat. Nos. 5,051,034 and RE 34,701 describe this type of construction anduse a ribbon of magnetic material to allow the conduit to be detected atthree to five feet underground. U.S. Pat. Nos. 5,006,086, 5,017,873 and5,114,517 use a magnetic ribbon that is spirally wound around theexterior surface of the conduit. Although the strip or ribbon in theseconstructions can be detected by conventional metal detecting equipment,it does not have a suitable construction for transmitting a toningsignal for extended distances and at the depths desired in the art.

As demonstrated above, there is a need in the art to provide a conduitthat can be detected by toning equipment for extended distances and atthe depths desired in the art. In addition, there is a need in the artto provide conduit that can be coupled to provide extended lengths ofunderground conduit that can be detected by toning equipment.

SUMMARY OF THE INVENTION

The present invention provides a conduit that can transmit a signal overgreat distances and that can therefore be readily detected by toningequipment. In addition, the conduit of the invention can be readilycoupled to provide extended lengths of conduit. In particular, thepresent invention uses a continuous wire to provide the toning signalthat is capable of being torn out through the conduit to allow theconduit to be coupled over extended lengths by forming an electricalconnection between the wire of adjacent segments of conduit. Inaddition, the connectors used for the conduit can be connected flushagainst the exterior surface of the conduit to prevent the leakage ofmoisture into the conduit and thus prevent damage to the cable withinthe conduit. The conduit of the invention also has excellent crushstrength as is desired in the art. The conductive wire also includes acoating that allows the conductive wire to be protected in theunderground environment and that facilitates the continuous productionof the conduit of the invention.

The above advantages are achieved through the use of a toneable conduitthat includes an elongate polymeric tube having a wall with an interiorsurface, an exterior surface, and a predetermined wall thickness. Achannel extends longitudinally within the wall of the elongate polymerictube and a stabilizing rib preferably extends longitudinally along theinterior surface of the wall of the elongate polymeric tube and islocated radially inward from the channel. A continuous wire iscoincident with the channel in the elongate polymeric tube and ispreferably coated with a coating composition that prevents the wire fromadhering to the polymer melt used to form the elongate polymeric tube.Preferably, the wire has a tensile strength of at least about 150 lbs.and is preferably a copper-clad steel wire, copper-clad aluminum wire,copper wire or tin copper wire. More preferably, the wire is copper-cladsteel wire. The wire also preferably has a diameter from about 0.32 mmto about 2.59 mm. More preferably, the wire has a diameter of 1.02 mm.In accordance with the invention, the wire is capable of transmitting atoning signal to allow the conduit to be detected by toning equipmentand is capable of being torn out of the polymeric tube to allow theconduit to be coupled. The wire is preferably coated with a coatingcomposition that is formed of a high melting temperature polymericmaterial, preferably having a melting temperature of at least about 500°F. Preferably, the high melting temperature polymeric material isselected from the group consisting of fluoropolymers, polyamides,polyesters, polycarbonates, polypropylene, polyurethanes, polyacetals,polyacrylics, epoxies and silicone polymers and is more preferablypolytetrafluoroethylene. Preferably, the conduit is formed ofpolyethylene or polyvinyl chloride and more preferably high-densitypolyethylene (HDPE). The conduit also preferably has a smooth exteriorsurface and can further include at least one additional rib (in additionto the stabilizing rib) extending longitudinally along the interiorsurface of the elongate polymeric tube to facilitate the installation ofcable within the conduit.

According to an alternative embodiment of the invention, the toneableconduit can further include a second channel that extends longitudinallywithin the wall of the elongate polymeric tube. A conductor can beprovided coincident with the second channel such as a continuous wirelike the one discussed above or a twisted pair of continuous wires toprovide a return path for signals that can be used to monitor the statusof the cable. A second stabilizing rib can also extend longitudinallyalong the interior surface of the wall of the elongate polymeric tubeand can be located radially inward from the second channel.

The present invention further includes a method of making toneableconduit, comprising the steps of advancing a continuous wire andextruding a polymer melt around the advancing wire in the form of anelongate polymeric tube having a wall of a predetermined thickness, aninterior surface, an exterior surface, and a stabilizing rib extendinglongitudinally along the interior surface of the wall of the elongatepolymeric tube such that the wire is embedded in the wall of theelongate polymeric tube and the stabilizing rib is located radiallyinward from the wire. In accordance with the invention, the advancingstep comprises advancing a wire coated with a coating composition thatprevents the wire from adhering to the polymer melt used in saidextruding step. Preferably, the polymer melt extruded into the form ofan elongate polymeric tube through the use of a die and a tip, wherein agroove in said tip forms the stabilizing rib on the interior surface ofthe conduit. A wire is preferably advanced through a wire guide tubeinto the polymer melt. A conductor such as an additional continuous wireor a twisted pair of continuous wires can also be advanced into thepolymer melt and the polymer melt extruded around the advancing wire andthe advancing conductor. The method of the invention can also includeforming additional ribs extending longitudinally along the interiorsurface of the elongate polymeric tube in the extruding step tofacilitate the installation of cable into the conduit. The wire that isadvanced into the polymer melt preferably has a tensile strength of atleast about 150 lbs. In particular, the wire is preferably a copper-cladsteel wire, copper-clad aluminum wire, copper wire or tin copper wireand is more preferably copper-clad steel wire, and preferably has adiameter of from about 0.32 mm to about 2.59 mm. The wire is alsopreferably coated with a coating composition formed of a polymericmaterial selected from the group consisting of fluoropolymers,polyamides, polyesters, polycarbonates, polypropylene, polyurethanes,polyacetals, polyacrylics, epoxies and silicone polymers. Preferably,the polymeric material has a melting temperature of at least about 500°F., and is more preferably polytetrafluoroethylene. The polymer melt ispreferably extruded in the form of an elongate polymeric tube having asmooth exterior surface.

The present invention also includes a method of coupling a firsttoneable conduit with a second toneable conduit, comprising the steps ofproviding a first toneable conduit as discussed above and providing asecond toneable conduit as discussed above, tearing the wire of thefirst toneable conduit through the exterior surface of the firsttoneable conduit, tearing the wire of the second toneable conduitthrough the exterior surface of the second toneable conduit,mechanically connecting the first and second toneable conduits, andelectrically connecting the wire from the first toneable conduit and thewire from the second toneable conduit. In addition, the first and secondtoneable conduits can include a second channel and a conductor such as asecond continuous wire or a twisted pair of continuous wires coincidentwith the second channel and the conductors in the first and secondtoneable conduits can also be torn through the exterior surface of thetoneable conduits and electrically connected with one another.

These and other features and advantages of the present invention willbecome more readily apparent to those skilled in the art uponconsideration of the following detailed description and accompanyingdrawings, which describe both the preferred and alternative embodimentsof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a toneable conduit according to thepresent invention.

FIG. 2 is a side view of the toneable conduit illustrated in FIG. 1according to the present invention.

FIG. 3 is a cross-sectional view of a toneable conduit according to analternative embodiment of the present invention further including anadditional continuous, high tensile strength wire.

FIG. 4 is a cross-sectional view of a toneable conduit according to analternative embodiment of the present invention further including atwisted pair of wires.

FIG. 5 schematically illustrates a method of making toneable conduitcorresponding to a preferred embodiment of the invention.

FIG. 6 is a cross-sectional view along line 4-4 of FIG. 3 illustratingthe interior of the crosshead used to form the conduit according to thepreferred embodiment of the invention.

FIG. 7 is a side view of the toneable conduit according to the presentinvention wherein the wire has been torn through the exterior surface ofthe conduit.

FIG. 8 is a side view of two adjacent coupled sections of conduit inaccordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings and the following detailed description, preferredembodiments are described in detail to enable practice of the invention.Although the invention is described with reference to these specificpreferred embodiments, it will be understood that the invention is notlimited to these preferred embodiments. But to the contrary, theinvention includes numerous alternatives, modifications and equivalentsas will become apparent from consideration of the following detaileddescription and accompanying drawings. In the drawings, like numbersrefer to like elements throughout.

FIGS. 1 and 2 illustrate a toneable conduit according to the presentinvention. As shown in these figures, the conduit is formed of anelongate polymeric tube 10 that includes a wall 12 having apredetermined thickness 14 and further includes an interior surface 16and an exterior surface 18. The exterior surface 18 is preferably smoothso that the conduit can be effectively coupled as discussed in moredetail below. The conduit can be formed of any suitable polymeric (i.e.plastic) material and suitable polymeric materials for conduit are knownin the art such as polyethylene or polyvinyl chloride. Preferably, theelongate polymeric tube 10 is formed of high density polyethylene(HDPE). The polymeric material can also be blended with certainadditives, e.g., for UV protection. The wall 12 of the elongatepolymeric tube 10 typically has a predetermined thickness 14 of fromabout 0.05 inches to about 0.75 inches. Moreover, the elongate polymertube 10 typically has a nominal inside diameter of from about 0.5 inchesto about 6.5 inches.

The toneable conduit preferably includes a stabilizing rib 20 thatextends longitudinally along the interior surface 16 of the elongatepolymeric tube 10. As shown in FIGS. 1 and 2, the stabilizing rib 20 isintegral with the elongate polymeric tube 10 and formed of the samematerial as the elongate polymeric tube. The stabilizing rib 20maintains the wall thickness 14 of the conduit when the wire is torn outof the conduit as discussed in more detail below such that it canwithstand the forces typically associated with installation, use andtransport of the conduit. Typically, the stabilizing rib 20 extends fromthe interior surface 16 of the elongate polymeric tube 10 such that thedistance 22 from the wire to the interior edge 23 of the stabilizing ribis at least equal to the wall thickness 14. The stabilizing rib 20 isalso located radially inward from the wire used in the invention. Thestabilizing rib 20 illustrated in FIGS. 1 and 2 has a generallysemicylindrical shape (i.e. an arcuate cross-section) but can have arectangular or trapezoidal shape, for example, so long as it providesthe desired amount of strength and stability to the conduit wall 12. Inaddition to the stabilizing rib 20, the conduit can include additionalribs (not shown) extending longitudinally along the interior surface 16of the elongate polymeric tube 10 and integral with the elongatepolymeric tube to facilitate the installation of cable in the conduit bydecreasing the surface area in contact between the interior surface ofthe elongate polymeric tube and the cable.

As shown in FIGS. 1 and 2, the toneable conduit includes a wire 24 thatextends longitudinally along the length of the elongate polymeric tube10 and is coincident with a channel the extends longitudinally withinthe wall 12 of the elongate polymeric tube 10. The wire 24 runscontinuously along the length of the elongate polymeric tube 10 and isembedded within the wall 12 of the elongate polymeric tube. Inparticular, the wire 24 is typically provided completely within the wall12 of the elongate polymeric tube 10. Preferably, the wire 24 extendsparallel to a central longitudinal axis A of the elongate polymeric tube10.

The wire 24 possesses sufficient tensile strength and elongation toallow the wire to be torn out through the exterior surface 18 of theelongate polymeric tube 10 (e.g., by using a pair of pliers). The wire24 used in the invention preferably has a tensile strength of at leastabout 150 lbs. as measured according to ASTM method B869. In addition,the wire 24 preferably has an elongation of at least about 1% asmeasured according to ASTM methods B3 and B869. The wire 24 ispreferably a copper-clad steel wire, copper-clad aluminum wire, copperwire or tin copper (tin-clad copper) wire. More preferably, the wire 24is a copper-clad steel wire. The wire 24 preferably has a diameter offrom 0.32 mm (28 gauge) to 2.59 mm (10 gauge), and more preferably is acopper-clad steel wire having a diameter of 1.02 mm (18 gauge).

As mentioned above, the wire 24 runs continuously along the length ofthe elongate polymeric tube 10 and thus it can transmit a toning signalalong the length of the conduit to allow the underground conduit to bedetected from the surface by toning equipment. Moreover, because of the“skin effect” associated with signal transmission as understood by thoseskilled in the art, the signal is transmitted along the outer surface 26of wire 24 and thus takes advantage of the conductivity of the copperportion present in the preferred wires used with the invention. As aresult, the wire 24 of the conduit can transmit signals over longdistances as desired in the art (e.g. at least 5 miles). It has beendiscovered that a larger diameter wire 24 (e.g. 18 gauge) transmits atoning signal over longer distances than a smaller diameter wire.Moreover, a larger diameter wire 24 is stronger than a smaller diameterwire and thus can more effectively be torn out of the conduit when it iscoupled with other conduit.

The wire 24 is coated with a layer 30 of a coating composition. Thecoating composition layer 30 typically has a thickness of from about 1to about 15 mils, and is more preferably about 8 mils. The coatingcomposition layer 30 is formed of a material that prevents the wire 24from adhering to the polymer melt used to form the elongate polymerictube 10. Accordingly, the coating composition layer 30 is typicallyformed of a polymeric material that has a melting temperature above thetemperature of the polymeric melt so that is does not melt during theformation of the elongate polymeric tube 10. Preferably, the coatingcomposition layer 30 is formed of fluoropolymers (e.g.polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene (FEP),ethylenetrifluoroethylene (ETFE), and ethylenechlorotrifluoroethylene(ECTFE), polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF));polyamides (e.g. nylon); polyesters (e.g. polyethylene terephthalate(PET)); polycarbonates; polypropylene; polyurethanes; polyacetals;polyacrylics; epoxies; silicone polymers; and mixtures thereof. The highmelting temperature polymeric materials used in the coating preferablyhas a melting temperature of at least about 500° F. More preferably, thecoating composition layer 30 is formed of a fluoropolymer and is morepreferably polytetrafluoroethylene (TEFLON®). Advantageously, becausethe wire 24 is coated with polytetrafluoroethylene, it also protects thewire 24 from the underground environment when it is torn out of theconduit and electrically connected to the wire from an adjacent conduitas discussed in more detail below. In particular, the coatingcomposition layer 30 preferably provides corrosion resistance to thewire 24.

Although not illustrated in FIGS. 1 and 2, the conduit of the inventioncan include one or more cables such as coaxial cables, fiber opticcables, twisted pair cables, electrical cables, support or messengercables, and the like. The advantages of the invention are particularlyevident when toning equipment is used to locate empty conduit (notincluding any cable) or conduit containing non-metallic cable such asfiber optic cable as metallic cable can be detected underground withoutthe need to use the conduit of the invention. Nevertheless, the conduitof the invention can be used to house metallic cable such as coaxialcable.

FIGS. 3 and 4 illustrate toneable conduits according to alternativeembodiments of the invention. As shown in FIGS. 3 and 4, the toneableconduit can further include a conductor such as a second continuous wire32 (FIG. 3) or a twisted pair of continuous wires 34 (FIG. 4) thatextends longitudinally along the length of the elongate polymeric tube10. The conductor is coincident with a channel that extendslongitudinally within the wall 12 of the elongate polymeric tube 10 andthat is typically different than the channel that is coincident with thewire 24. The conductor runs continuously along the length of theelongate polymeric tube 10 and is embedded within the wall 12 of theelongate polymeric tube. In particular, the conductor is typicallyprovided completely within the wall 12 of the elongate polymeric tube10. Preferably, the conductor extends parallel to a central longitudinalaxis A of the elongate polymeric tube 10. As shown in FIGS. 3 and 4, thetoneable conduit can also include a stabilizing rib 33 that is locatedradially inward from the conductor used in the invention in the samemanner as the stabilizing rib 20.

Like the wire 24, the wire 32 illustrated in FIG. 3 possesses sufficienttensile strength and elongation to allow the wire to be torn out throughthe exterior surface 18 of the elongate polymeric tube 10. The wire 32preferably has a tensile strength of at least about 150 lbs. as measuredaccording to ASTM method B869. In addition, the wire 32 preferably hasan elongation of at least about 1% as measured according to ASTM methodsB3 and B869. The wire 32 is preferably a copper-clad steel wire,copper-clad aluminum wire, copper wire or tin copper (tin-clad copper)wire. More preferably, the wire 32 is a copper-clad steel wire. The wire32 preferably has a diameter of from 0.32 mm (28 gauge) to 2.59 mm (10gauge), and more preferably is a copper-clad steel wire having adiameter of 1.02 mm (18 gauge). The wire 32 is also preferably coatedwith a layer of a coating composition 35 like the coating compositiondescribed above with respect to the wire 24.

Each of the wires 36 and 37 in the twisted pair of continuous wires 34illustrated in FIG. 4 preferably has sufficient tensile strength andelongation to allow the twisted pair of wires to be torn out through theexterior surface 18 of the elongate polymeric tube 10. For example, thecontinuous wires 36 and 37 used in the twisted pair of continuous wires34 can be formed of the wire described above with respect to the wire24. In addition, the wires 36 and 37 are also preferably coated with alayer of a coating composition 38 and 39 like the coating compositiondescribed above with respect to the wire 24.

As mentioned above, the wire 32 and the twisted pair of wires 34 runcontinuously along the length of the elongate polymeric tube 10. Thus,the wire 32 and the twisted pair of wires 34 can provide a return pathfor signals that can be used to monitor the status of the cable. Forexample, the wire 32 and the twisted pair of wires 34 can be used withtime-domain reflectometer (TDR) devices to determine if there are damagepoints along the length of the conduit. As is well understood to thoseskilled in the art, TDR devices are meters with an oscilloscope-typedisplay that send out a pulse along a line of cable and that measuresany inconsistencies in the cable. The pulse is reflected back toaccurately determine where a break or other problem is in the cable. TheTDR devices greatly reduce the time that would otherwise be needed tophysically locate problems in the cable.

FIG. 5 illustrates the preferred method embodiment for producing thetoneable conduit of the invention. As shown in FIG. 5, the wire 24 istaken from a supply reel 40 and is fed through a wire guide 42. The wire24 then passes through a lubrication apparatus 44 that lubricates thewire for further downstream processing. The lubricated wire 24 thenadvances into a crosshead 46, which communicates with an extruderapparatus 48 via a flow channel (not shown). Although not illustrated inFIG. 5, a second wire 32 or a twisted pair of wires 34 can also be takenfrom a supply reel (not shown), fed through a wire guide, lubricated andadvanced into the crosshead 46 in the manner described herein withrespect to the wire 24 to produce the toneable conduits illustrated inFIGS. 3 and 4.

The polymeric materials and any additives such as colorants that areused to form the elongate polymeric tube 10 (and stabilizing rib 20) arefed to the extruder apparatus 48, e.g., through a hopper (not shown). Inthe preferred embodiment of the invention, the polymeric materialsinclude HDPE as discussed above. The extruder apparatus 48 operates atan elevated temperature above the melting temperature of the polymericmaterials used to form the elongate polymeric tube 10 to provide apolymer melt. For example, in the preferred embodiment of the inventionwherein the conduit is formed of HDPE, the extruder apparatus 48 isoperated at a temperature of from about 300° F. to about 500° F.

FIG. 6 illustrates the formation of the conduit of the invention in moredetail. A wire guide tube 50 delivers the wire 24 to an annular gap 52between a tip 54 and a die 56 of the crosshead 46 while the extruderapparatus 48 delivers the polymer melt to the annular gap through a flowchannel (not shown). The tip 54 and the die 56 form the annular gap 52and shape the polymer melt into a tubular configuration to form theelongate polymeric tube 10. In particular, the tip 54 provides the shapeof the interior surface 16 of the elongate polymeric tube 10 while thedie 56 provides the shape of the exterior surface 18 of the elongatepolymeric tube. A groove 60 provided in the tip 54 forms the stabilizingrib 20 in the conduit. Although not shown, additional grooves can beprovided in the tip 54 to provide additional ribs along the interiorsurface 16 of the elongate polymeric tube 10 to facilitate theinstallation of cable in the conduit. The polymer melt forms around thewire 24 and the wire becomes embedded in the wall 12 of the elongatepolymeric tube 10. The coating composition layer 30 on the wire 24 andthe lubricant applied to the wire advantageously prevent the wire 24from sticking to the polymer melt and facilitate the formation of theconduit of the invention.

Referring again to FIG. 5, the conduit leaves the crosshead 46 andadvances to a cooling trough 62 that utilizes water to cool the conduitto allow it to harden. The conduit is then advanced to a take-up reel64. The conduit can be stored or shipped on the take-up reel 64 and canreadily be installed by unwinding the conduit from the take-up reel.

As mentioned above, the conduit of the invention can be readily coupledwith other conduit. In particular, as shown in FIG. 7, the wire 24 canbe torn out through the exterior surface 18 of the elongate polymerictube 10 by applying a force on the wire perpendicular to the axis A in adirection 62. As discussed above, the preferred wire 24 used inaccordance with the invention has sufficient tensile strength andelongation to tear through the HDPE conduit. Once the wire 24 is tornout through the conduit, the conduit can be coupled with an adjacentconduit.

As shown in FIG. 8, a first conduit 70 is coupled with a second conduit72. A conduit connector 74 is fitted onto the first conduit 70 and thesecond conduit 72 to provide a connection between adjacent segments ofconduit. A wire 76 torn out of the first conduit 70 and a wire 78 tornout of the second conduit 72 are electrically connected or coupledtogether through the use of a suitable device such as the electricalconnector 80. If the first conduit 70 and the second conduit 72 includea wire 32 or a twisted pair of wires 34 as illustrated in FIGS. 3 and 4,the wire or twisted pair of wires can also be torn through the conduitsand electrically connected in the manner described with respect to thewires 76 and 78. In accordance with the invention, because the conduitof the invention has a smooth exterior surface, the conduit connector 74fits flush to the exterior surfaces of the first conduit 70 and secondconduit 72. As is understood in the art, the first conduit 70, secondconduit 72, conduit connector 74, wire 76, wire 78 and electricalconnector 80 can optionally be wrapped by a shrink wrap film that isheated to allow it to shrink around the conduit to prevent the ingressof moisture into the conduit along the conduit connector 74.

The conduit of the invention can advantageously be detected withconventional toning equipment used in the art. In particular, when theconduit of the invention is buried underground, even if it is empty orcontains a non-metallic cable, it can be detected by toning equipment bytransmitting a signal along the wire 24 and detecting the signal fromthe ground surface. As a result, the conduit of the invention can bedetected at levels at deep as 10 feet underground or even at greaterdepths through the use of toning equipment. Moreover, the conduit of theinvention can also be detected by metal detecting equipment at the lowerunderground depths (e.g. 3-5 feet) where those types of devices areuseful. In addition to being detectable by toning equipment, i.e.,toneable, because the conduit of the invention can be readily coupled asdiscussed above, the conduit of the invention can be detectedunderground over extended lengths, e.g., 5 to 10 miles, as desired inthe art. Furthermore, the conduit can include a wire 32 or a twistedpair of wires 34 and can be used to provide a return path for signals todetermine if damage points exist along the cable.

It is understood that upon reading the above description of the presentinvention and reviewing the accompanying drawings, one skilled in theart could make changes and variations therefrom. These changes andvariations are included in the spirit and scope of the followingappended claims.

1. A toneable conduit, comprising: an elongate polymeric tube having awall with an interior surface, an exterior surface, and a predeterminedwall thickness; and a first channel extending longitudinally within thewall of the elongate polymeric tube; and a continuous wire coincidentwith the first channel in the elongate polymeric tube, said wire beingcoated with a coating composition that prevents the wire from adheringto the polymer melt used to form the polymeric tube; said continuouswire capable of transmitting a toning signal to allow the conduit to bedetected by toning equipment and capable of being torn out of thepolymeric tube and remaining continuous to allow the conduit and wire tobe coupled.
 2. The toneable conduit according to claim 1, furthercomprising a first stabilizing rib extending longitudinally along theinterior surface of the wall of the elongate polymeric tube and locatedradially inward from said channel.
 3. The toneable conduit according toclaim 2, further comprising at least one additional rib extendinglongitudinally along the interior surface of the elongate polymeric tubeto facilitate the installation of cable within the conduit.
 4. Thetoneable conduit according to claim 1, wherein the coating compositionis formed of a polymeric material selected from the group consisting offluoropolymers, polyamides, polyesters, polycarbonates, polypropylene,polyurethanes, polyacetals, polyacrylics, epoxies and silicone polymers.5. The toneable conduit according to claim 4, wherein the coatingcomposition is formed of a polymeric material that has a meltingtemperature of at least about 500°F.
 6. The toneable conduit accordingto claim 5, wherein the coating composition is formed ofpolytetrafluoroethylene.
 7. The toneable conduit according to claim 1,wherein the continuous wire has a tensile strength of at least about 150lbs.
 8. The toneable conduit according to claim 7, wherein thecontinuous wire is selected from the group consisting of copper-cladsteel wire, copper-clad aluminum wire, copper wire, and tin copper wire.9. The toneable conduit according to claim 7, wherein the continuouswire is copper-clad steel wire.
 10. The toneable conduit according toclaim 7, wherein the continuous wire has a diameter of from about 0.32mm to about 2.59 mm.
 11. The toneable conduit according to claim 1,wherein the exterior surface of the tube is smooth.
 12. The toneableconduit according to claim 1, further comprising a second channelextending longitudinally within the wall of the elongate polymeric tubeand a conductor selected from the group consisting of a continuous wireand a twisted pair of continuous wires coincident with the secondchannel in the elongate polymeric tube.
 13. The toneable conduitaccording to claim 12, further comprising: a first stabilizing ribextending longitudinally along the interior surface of the wall of theelongate polymeric tube and located radially inward from said firstchannel; and a second stabilizing rib extending longitudinally along theinterior surface of the wall of the elongate polymeric tube and locatedradially inward from the second channel.
 14. A toneable conduit,comprising: an elongate polymeric tube formed of high densitypolyethylene having a wall with an interior surface, an exteriorsurface, and a predetermined wall thickness; a channel extendinglongitudinally within the wall of the elongate polymeric tube; and astabilizing rib extending longitudinally along the interior surface ofthe wall of the elongate polymeric tube and located radially inward fromsaid channel; and a continuous, copper-clad steel wire coincident withthe channel in the elongate polymeric tube, said copper-clad steel wirecoated with polytetrafluoroethylene to prevent the wire from adhering tothe polymer melt used to form the polymeric tube; said copper-clad steelwire capable of transmitting a toning signal over long distances toallow the conduit to be detected by toning equipment and capable ofbeing torn out of the polymeric tube and remaining continuous to allowthe conduit and wire to be coupled.
 15. A toneable conduit, comprising:an elongate polymeric tube having a wall with an interior surface and anexterior surface; and a first channel extending longitudinally withinthe wall of the elongate polymeric tube; and a continuous wirecoincident with the first channel in the elongate polymeric tube; saidcontinuous wire being a toning signal wire allowing the conduit to bedetected by toning equipment and said wire capable of being torn out ofthe polymeric tube and remaining continuous to allow the conduit andwire to be coupled.
 16. The toneable conduit according to claim 15,further comprising a first stabilizing rib extending longitudinallyalong the interior surface of the wall of the elongate polymeric tubeand located radially inward from said channel.
 17. The toneable conduitaccording to claim 16, further comprising at least one additional ribextending longitudinally along the interior surface of the elongatepolymeric tube to facilitate the installation of cable within theconduit.
 18. The toneable conduit according to claim 15, wherein thecontinuous wire has a tensile strength of at least about 150 lbs. 19.The toneable conduit according to claim 18, wherein the continuous wireis selected from the group consisting of copper-clad steel wire,copper-clad aluminum wire, copper wire, and tin copper wire.
 20. Thetoneable conduit according to claim 18, wherein the continuous wire iscopper-clad steel wire.
 21. The toneable conduit according to claim 18,wherein the continuous wire has a diameter of from about 0.32 mm toabout 2.59 mm.
 22. The toneable conduit according to claim 15, whereinthe continuous wire is selected from the group consisting of copper-cladsteel wire, copper-clad aluminum wire, copper wire, and tin copper wire.23. The toneable conduit according to claim 15, wherein the continuouswire is copper-clad steel wire.
 24. The toneable conduit according toclaim 15, wherein the continuous wire has a diameter of from about 0.32mm to about 2.59 mm.
 25. The toneable conduit according to claim 15,wherein the wall has a predetermined thickness.
 26. The toneable conduitaccording to claim 25, wherein the exterior surface of the tube issmooth.
 27. The toneable conduit according to claim 15, furthercomprising a second channel extending longitudinally within the wall ofthe elongate polymeric tube and a conductor selected from the groupconsisting of a continuous wire and a twisted pair of continuous wirescoincident with the second channel in the elongate polymeric tube. 28.The toneable conduit according to claim 27, further comprising: a firststabilizing rib extending longitudinally along the interior surface ofthe wall of the elongate polymeric tube and located radially inward fromsaid first channel; and a second stabilizing rib extendinglongitudinally along the interior surface of the wall of the elongatepolymeric tube and located radially inward from the second channel. 29.A toneable conduit, comprising: an elongate polymeric tube formed ofhigh density polyethylene having a wall with an interior surface, anexterior surface, and a predetermined wall thickness; a channelextending longitudinally within the wall of the elongate polymeric tube;and a continuous, copper-clad steel wire coincident with the channel inthe elongate polymeric tube; said copper-clad steel wire being a toningsignal wire allowing the conduit to be detected by toning equipment andsaid wire capable of being torn out of the polymeric tube and remainingcontinuous to allow the conduit and wire to be coupled.
 30. The toneableconduit according to claim 29, wherein said polymeric tube furthercomprises a stabilizing rib extending longitudinally along the interiorsurface of the wall of the elongate polymeric tube and located radiallyinward from said channel.
 31. The toneable conduit according to claim29, wherein said copper-clad steel wire is coated withpolytetrafluoroethylene.
 32. A toneable conduit, comprising: an elongatepolymeric tube having a wall with an interior surface and an exteriorsurface; and a first channel extending longitudinally within the wall ofthe elongate polymeric tube; and a continuous wire coincident with thefirst channel in the elongate polymeric tube, said wire being coatedwith a coating composition that prevents the wire from adhering to thepolymer melt used to form the polymeric tube; said continuous wire beinga toning signal wire allowing the conduit to be detected by toningequipment and said wire capable of being torn out of the polymeric tubeand remaining continuous to allow the conduit and wire to be coupled.33. A toneable conduit, comprising: an elongate polymeric tube having awall with an interior surface, an exterior surface, and a first channelextending longitudinally within the wall of the elongate polymeric tube;and a continuous wire having a tensile strength of at least about 150lbs coincident with the first channel in the elongate polymeric tube;said continuous wire being a toning signal wire allowing the conduit tobe detected by toning equipment.